<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
      const arr = ["jack", 20, true];

      console.log(arr);
      arr[0] = "lili";
      arr[1] = 21;
      arr[2] = false;
      console.log(arr);
      console.log(arr.length);

      /* 
      const arr = {
        0: "jack",
        1: 20,
        2: true
      }
      */
    </script>
  </body>
</html>
